Since a lot of dotted lines (such as splitters and borders in UI design) will be used in practical drawing, I would like to share here 4 dotted line drawing methods that I have concluded by myself.

The first one: the most straightforward and time-consuming drawing method.

We take the tool “pencil” as an example. Here is an amplified pixel grid to help explain. Because the pencil tool is edge-sharpened and will not leave extra trimmings when drawing, so it is suitable for drawing lines that require high pixel accuracy, but not fit for drawing straight lines.

Step 1, Draw the dotted line part. Draw a 4xl line segment here.
Step 2, Use “Marquee tool” frame to select drawn pixels.
Step 3, Press “Ctrl+Alt+T” to get an option bar as shown in the following picture. Now make sure the triangle is in the state of being selected and input shift values into the X value input box. If you want the clearance part of the dotted line as 3px, input 7 (because the length of the dotted line is 4px). At this point, the line segment will move 7px to the right when copying. Then press “Enter” completes the change.
Step 4, Now make sure it is still in the state of box and continuously press down “Shift+Ctrl+Alt+T” to copy the line segment infinitely and attain a dotted line with a 4px solid line segment and 3px clearance.
Step 5, You can have many variation by using this method.
PS: select pixel with “Marquee tool” before making changes so as to keep only one layer when making duplicate transformation and reduce the number of layers.

The second one: it is a more flexible and time-saving drawing method.

This method is especially for the “pencil” tool and the diameter of the brush should not exceed 2px.

Step 1, If you want to draw dotted lines with only dots, press F5 to open the brush plate; set the “Spacing” value as more than 200% and in round figure in the “Shape Dynamic” option; now let’s set a value to test the effect.
Step 2, If you want to draw a 2px dotted line with 2px clearance, draw a dotted line with 400% spacing at firstly; shift to the state of selecting tools; press down “Alt” and “→” at the same time to copy the line segment; meanwhile, move 1px to the right, and combine the two layers.
PS: This method is also applied to drawing dotted lines with different sizes of solid lines and clearances.

The third one: use dual brush; it is especially for the brush tool.

Step 1, Press F5 to open the brush plate and set values as shown in the following graphic.
Step 2, Set “Dual Brush” as shown in the following graphic.
Step 3, Please see the drawing effect as shown in the following graphic.
Step 4, To understand the above parameters straightforwardly, I have drawn a diagram here.
PS: this method is flexible and easy to take control. It can also be used in stroke. When the dual brush is set, the line can also be stored as “Brush Presets” to facilitate using in future.

The fourth one: use Photoshop CS6; this method is most straightforward and easiest to understand.

Step 1, Use the shape tool or the pen tool to draw a frame.
Step 2, Select the frame, set the “Fill” as null, the “Stroke” as white and the stroke width as 1px, as shown in the graphic:
Step 3, The key step; click “Stroke Options”, select dotted line pattern and click “More Options” to get options of the stroke; input values of the dotted line and the clearance.
Step 4, Finally, draw the effect drawing as shown in the following graphic.
PS: to get richer patterns, please continue to set other values of the dotted line and the clearance. You can also draw lines through drawing non-closed shapes.

Every method has its advantages and disadvantages. You should select according to designing requirements. Thank you for reading.